KMP

Posted 2021-01-19 codemaker-li

啥也不说了

上代码：

#include <cstdio>
#include <iostream>
#include <string>
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef double db;

#define MAXN 100010
char a[MAXN],b[MAXN];
int next[MAXN],f[MAXN];
int n,m,ans;

int main () {
    cin>>b;//长串 
    cin>>a;//短串
    n=strlen(a);
    m=strlen(b);
    next[1]=0;
    for (int i=2,j=0;i<=n;i++) {
        while (j>0&&a[i]!=a[j+1]) {
            j=next[j];
        }
        if (a[i]==a[j+1]) j++;
        next[i]=j;
    } 
    for (int i=1,j=0;i<=m;i++) {
        while (j>0&&(j==n||b[i]!=a[j+1])) j=next[j];
        if (b[i]==a[j+1]) j++;
        f[i]=j;
        if (f[i]==n-1) ans++;
    }
    cout<<ans<<endl;
    return 0;
}